A well-known waste product of the phosphate fertilizer industry is silicon tetrafluoride. Silicon tetrafluoride in this context is a gaseous by-product of common phosphate rock and acid reactions that are used to produce soil fertilizers. The most common phosphate rock used as a source mineral for production of soil fertilizers contains, on a dry weight basis, appreciable portions of fluoroapatite Ca.sub.10 F.sub.2 (PO.sub.4).sub.6 and silica SiO.sub.2. Upon reaction with acids such as phosphoric or sulfuric acid, silicon tetrafluoride is released: EQU SiO.sub.2 +Ca.sub.10 F.sub.2 (PO.sub.4).sub.6 +H.sub.2 SO.sub.4 .fwdarw.CaH.sub.4 (PO.sub.4).sub.2 +Ca(SO.sub.4).multidot.H.sub.2 O+SiF.sub.4
The silicon tetrafluoride released is generally accompanied by hydrogen fluoride, water vapor, gaseous oxides of sulfur and nitrogen. As noted in Table 1, the major U.S. deposits of phosphate rock contain SiO.sub.2 and F and the average yield of fluorine is about 230 lbs per ton of fertilizer produced.
TABLE 1 __________________________________________________________________________ Representative Analyses of Commerical Phosphate Rocks Organic Location and type P.sub.2 O.sub.5 CaO MgO Al.sub.2 O.sub.3 Fe.sub.2 O.sub.3 SiO.sub.2 SO.sub.3 F Cl CO.sub.2 carbon Na.sub.2 O K.sub.2 O H.sub.2 __________________________________________________________________________ O United States Florida land pebble, high grade 35.5 48.8 0.04 0.9 0.7 6.4 2.4 4.0 0.01 1.7 0.3 0.07 0.09 1.8 land pebble, furnace grade 30.5 46.0 0.4 1.5 1.9 8.7 2.6 3.7 0.01 4.0 0.5 0.1 0.1 2.0 hard rock, high grade 35.3 50.2 0.03 1.2 0.9 4.3 0.1 3.8 0.005 2.8 0.3 0.4 0.3 2.0 hard rock, waste pond 23.0 28.5 0.4 14.8 2.9 19.8 0.01 2.1 0.005 1.4 0.3 0.1 0.4 7.0 Tennessee brown rock, high grade 34.4 49.2 0.02 1.2 2.5 5.9 0.7 3.8 0.01 2.0 0.2 0.3 1.4 brown rock, furnace grade 21.2 29.1 0.6 10.0 6.2 25.6 0.4 2.2 1.2 0.3 0.3 0.4 2.5 Western States phosphoria rock, high grade 32.2 46.0 0.2 1.0 0.8 7.5 1.7 3.4 0.02 2.1 1.8 0.5 0.4 2.5 phosphoria rock, low grade 19.0 23.3 1.4 5.9 4.0 27.4 1.9 1.8 4.0 5.0 1.5 1.0 3.5 __________________________________________________________________________
Table 2 shows the resulting fluorine yields for various annual consumption rates.
TABLE 2 ______________________________________ FLUORINE SUPPLIES FROM PHOSPHATE ROCK MINERALS Average Estimated Estimated Fertilizer Fluorine Reserves Production Release Location (Long Tons) Long Tons/Yr. Long Tons/Yr. ______________________________________ United States 14 .times. 10.sup.9 20 .times. 10.sup.6 600,000 North Africa 25 .times. 10.sup.9 13 .times. 10.sup.6 390,000 U.S.S.R. 8 .times. 10.sup.9 9 .times. 10.sup.6 270,000 Oceania 0.2 .times. 10.sup.9 2.3 .times. 10.sup.6 69,000 Brazil 0.6 .times. 10.sup.9 0.6 .times. 10.sup.6 18,000 U.A.R. 0.2 .times. 10.sup.9 0.6 .times. 10.sup.6 18,000 All Other 0.7 .times. 10.sup.9 4.5 .times. 10.sup.6 135,000 TOTALS 48.7 .times. 10.sup.9 50 .times. 10.sup.6 1.5 .times. 10.sup.6 ______________________________________
Another emerging source of fluorine is in the recovery of oil from shale or dolamite reserves. Fluorine available in the petrorock minerals is considered a bothersome interferant to oil recovery operations. The present invention contemplates using the hydrocarbon and fluorine constituents of petrorock minerals to form useful precursors for the production of architectural polymers. The present invention also contemplates apparatus used in the production of such architectural polymers.
The subject invention concerns recovery of the fluorine and conversion to new and useful polymers and feedstocks by novel coal or petrorock gasification process and apparatus. This invention overcomes the major problems that have defeated past efforts to economically recover fluorine from phosphate fertilizer waste streams. The problems as set out in detail in pages 1525-1528 of Ind. Eng. Chem. 50, (1958) by G. Tarbutton, T. O. Farr, T. M. Jones, and H. T. Lewis Jr., include the fact that the greatest percentage of fluorine values are set out as silicon tetrafluoride. The chemical stability of silicon tetrafluoride, based upon the high free energy of formation is sufficient to make it difficult to convert the fluorine present to hydrogen fluoride, and although several flow charts for this conversion have been tested they are not economically viable. Among the objects of the present invention are the following:
1. To develop a valuable by-product of the phosphate fertilizer industry.
2. To avoid contamination of the atmosphere by fluorine compounds that destroy ozone.
3. To develop petrorock and coal gasification treatments to provide useful products.
4. To provide a new method for extracting a desired monomer from several chemical species.
5. To provide new thermoplastic polymers having improved chemical and physical properties.
6. To provide apparatus for accomplishing the aforesaid methods which is effective in operation and economical to manufacture and maintain.